DE2235408A1 - ELECTROPHOTOGRAPHIC RECORDING MATERIAL - Google Patents

Description

Priority: Great Britain, June 20, 1971, note no. 34-046/71

This invention relates to an electrophotographic recording material and its use in manufacture photographic images.

Binder-type photoconductive layers formed by • including a finely divided photoconductor in a binder are well known *

Usually, electrophotographic materials are made with a photoconductive layer is used which contains photoconductive zinc oxide dispersed in an insulating binder is. The layer is applied to a sufficiently conductive substrate, e.g. a paper coated with clay or glassine paper, from a color-like coating mixture according to common paper coating techniques.

Since the zinc oxide has a bright white color, it forms an excellent contrast base with the developer materials applied to it. In addition, zinc oxide is relatively cheap and can be spectrally sensitized by many dyes. However, as has already been explained in British Patent 1,256,888, the positive corona charging of photoconductive zinc oxide base layers is only of an acceptable level if photoconductive zinc oxide is used which has been treated with "a special chemical compound" iutj 'lic; his positive Auf Ladbarkeü; vnvb'Hiiiurb.

^ü? ^ - ' ⁷ 209Bi) egg / 1212

A-G 100.5

The present invention is based on the knowledge that electrophotographic recording materials, which are photoconductive Containing zinc oxide, to see electrophotography Positive charge recording purposes can be applied through the use of a mixture of photoconductive particles and colorless or white »positive chargeable pigment particles in the photoconductive binder layer in a weight ratio that Heiner as 50:50, but not less than 10:90.

Preferred mixtures of dispersed photoconductive Zinc oxide and positively chargeable particles have a weight ratio of 30:70 to 40:60.

It should be noted that the positively chargeable particles need not be photoconductive and that both inorganic as well as organic, finely divided, positively chargeable particles

• Can be used.

In order to select the positively chargeable particles, an experiment has been developed according to which the particles in question in a weight ratio of 50 to 95 % in an insulating binder having a specific resistance of at least

10 0hm.cm dispersed and applied to a conductive base so that a layer of 10 to 30 microns is formed will.

The applied layer is exposed to a positive corona charge of +6000 volts in the dark, up to a maximum

Voltage level is reached.

Layers produced and treated in this way, which after completion the charging at least 5 seconds in the dark a positive charge with a potential difference of at least 200 volts in terms of a conductive one in contact with it TrägoL'ii withhold contain pigments that are useful for the Purpose of the present invention suitable π Ind.

Dor Dunku lubful L we <l κ .Η. average a. ·? Electric motor »with GV.557

"vibrating electrode as described by CJ Young and HG Greig (ECA Review (195 ² O, 27, 469), connected to a Bruel + Ejaer voltage level recorder.

Substances which meet the criteria of the abovementioned experiment and are advantageous for the purpose of the present invention used in conjunction with photoconductive zinc oxide include:

- barium sulfate

- zinc sulfide

- silica (SiC ^)

- polyethylene

- magnesium oxide

- titanium (IV) dioxide

- calcium carbonate

- zinc monobuty! Phosphate

- corn starch

- water-repellent starch

- albumin

- anthracene

- naphthalene

- benzophenone

- diphenyl

The grain size of the added substances advantageously corresponds about that of the photoconductive zinc oxide particles, but can vary widely, e.g., from 10 microns to 20-50 microns.

The grain size of the photoconductive zinc oxide is e.g. 0.1 to 15 microns.

In a mixture with a suitable, insulating binder or a binder mixture possesses the recording layer preferably a specific resistance that is approximately

7 14 is between 10 ' and 10 0hm.cm.

The recording layer can be between 50 and 97% by weight of the contain dispersed particles with respect to the binder.

GV.557

209885/1232

A preferred weight ratio of the binder to the « dispersed particles is between 1: 4- and 1:10.

Any polymeric or resinous binder or mixture of polymeric binders suitable for the use in electrophotographic recording layers containing photoconductive zinc oxide is already known

are.

Suitable binders have a resistance higher than the inherent resistance of the photoconductive zinc oxide particles is. In this regard, for example, electrically insulating, organic, resinous "binders of the polyurethane type, Polyesters, polycarbonates, polystyrenes, chlorinated rubber, acrylic resin, alkyd resins or vinyl acetate copolymers, e.g. Vinyl chloride acetate resin is used.

According to the casting composition, the layers are made of binder and pigment made from an organic solvent or a solvent mixture made from an emulsion of organic solvents Solvents and water or applied from an aqueous medium.

Particularly suitable binder combinations for application from organic solvents are described in the British patent 1 199 061.

Photoconductive coating compositions coated from an aqueous emulsion are disclosed, for example, in U.S. Patent 3,152 described.

Photoconductive casting compositions from an alkaline, aqueous binder solutions are disclosed, for example, in British Patents 1,125,579 and 1,125,580 and in U.S. Patent 3 160 503 described.

According to a particular embodiment, the binder or the binder composition has a specific one Resistance lower than that of photoconductive zinc oxide grains treated with a compound, as in British Patents 1,020,504 and 1,020,506

GV. 557 209885/1232

■ was described.

According to the inventions described in these patents it has been found that the zinc oxide can be given sufficient dark resistance to make it unnecessary is to use a binder with a high dark resistance when forming a photoconductive zinc oxide layer. Preferred compounds for treating the photoconductive zinc oxide grains and increasing their dark resistance are Acid ester derivatives of oxo acids of phosphorus, e.g. mono- and dibutyl orthophosphate.

Other compounds that reduce the dark resistance of the photoconductive Enhancing zinc oxide grains are urazole, urazole derivatives and analogous compounds used in the UK U.S. Patent 1,256,888 and U.S. Patent 3,634,080 have been described. These compounds correspond to the following general formula:

fc N- ₂

in which:

] L · and Eo jectes a hydrogen atom, an alkyl group including a substituted alkyl group, an aryl group including a substituted aryl group, an acyl group including a substituted acyl group, eg an aliphatic acyl group (Alkoyl) or substituted, aliphatic acyl group, eg an acetyl group or an aromatic Acyl group (aroyl), for example a benzoyl group including a substituted, aromatic acyl group or a heterocyclic input including a substituted, heterocyclic input, e.g. a pyridine ring or a thiazole ring ^ or E ^ and E ₂ together represent the necessary atoms to form a fused-in or to form a fused ring system. ".

GV.557 -

209885/1232

Z the atoms that are necessary to make a 5- or 6-membered To close a ring, including such a ring

in substituted form and including such a ring which is part of a substituted or not substituted, attached ring system, X represents an oxygen atom or imino,

wherein at least one of the nitrogen atoms forming a part of the ring that is closed by Z, carries a hydrogen atom, which can optionally be replaced by a cation can if the compound is used in salt form.,

These compounds, which increase the dark resistance, are preferred in conjunction with the photoconductive zinc oxide Amounts from 0.01 to 10% by weight are used.

In the manufacture of the electrophotographic material according to the present invention, in practice, any one may be commercially available • Available white zinc oxide, e.g. produced by oxidation of zinc vapor (French process), is used will.

Particularly suitable types of zinc oxide are:

- Zinc oxide, which is sold under the trade name BLANC DE ZINC Neige extra pure, types A, B and C (from Vieille Montagne S.A., Liège, Belgium), and

Zinc oxide sold by Durham Chemical Ltd., Birtley, England under the trade names MICROX and ELEKTROX.

In addition to one or more binders, the positively chargeable particles, the photoconductive zinc oxide grains and the compounds that increase dark resistance, the recording layers of the present invention can use any of them contain known additives, e.g. compounds that improve strength, gloss, viscosity and thermal stability affect and compounds that affect the spectral sensitivity and / or the general sensitivity of the recording layer raise.

Examples of suitable, spectral sensitizers,

209885/1232

which the spectral sensitivity of the photoconductive Increase zinc oxide are described in "British Patents 1,020,504, 1,199,062, 1,200,901, 1,183,044 and 1,198,994. -

About the color of the applied spectral sensitizer To mask, dyes can be used which are complementary in color to the sensitizer and the recording layer have a non-white appearance as described, for example, in British Patent 1,142,509 became. - ·.

According to a preferred embodiment of the invention Production of photoconductive recording material are both the photoconductive zinc oxide particles and the positively chargeable particles homogeneously dispersed in a solution containing the dissolved, insulating binder (s), the dispersion obtained being applied to an electroconductive support.

Various techniques can be used to apply the photoconductive layer, e.g. application by spinning, Spraying, brushing, Eo11 coating, dip coating, Bakel coating or by means of an extruder.

The layer formed is e.g. or infrared radiation dried.

The support for the recording layer preferably has a specific resistance which is 100 ml less than that of the dried recording layer in the dark. In general, its specific resistance is less than 1θ "0hm.cm, but preferably less than ΙΟ- ⁷ 0hm.cm.

The supports can be made of metal or resin films coated with conductive layers or Paper carriers that contain conductive substances and / or are coated with conductive intermediate layers. Particularly suitable paper supports are those that have a high level of impermeability

GV.557

209885/1232

[Permeability to organic solvents, such as glassine paper, according to British patent specification 995 4-91

Sheets of paper that have insufficient electrical conductivity are coated or impregnated with substances, which increase their conductivity, e.g. by means of a conductive, polymeric coating or by means of a metal foil, e.g. a Paper laminated aluminum foil.

Substances that are suitable for the conductivity of a sheet of paper and which can be used in the pulp are hygroscopic compounds and antistatic Agents such as those described in British Patent 964-877 and polyionic antistatic agents Type, e.g. CALGON CONDUCTIVE POLYMER, 261 (registered trademark of Calgon Corporation, Inc., Pittsburgh, Pa., USA, for a solution containing 39.1% by weight active, conductive solids and a conductive polymer with repeating Contains units of the following type):

H ₂ C CH

H ₀ C \ e 2, ι

-HC CH

Cl "

2 "

Electrophotographic materials according to the present invention can be used in any for recording using Techniques used in photoconductors can be used.

Recording materials according to the present invention can be used in both a recording technique that contains a negative corona charge as well in a recording technique with a positive corona charge.

? OUHH! ") / 1? 3 ?

Thanks to this property it is possible to use one and the same Developer, e.g., an electrophoretic developer with toner particles having e.g. a positive charge, and the same original as desired to reproduce as a positive or negative copy, whatever the sign of the electrostatic Charge depends on which of the recording layer of the recording material was given.

Assuming a microfilm image is the original, it is therefore possible, for example, both positive and negative, enlarged copies of the original with one and the same developer using recording materials of the present invention.

The following examples illustrate the present invention.

example 1

The improved, positive chargeability and recording properties of photoconductive recording materials, which contains zinc sulfide in an amount suitable for the purpose of this invention is evidenced by the following series of comparative tests.

For reasons of comparison, the following casting compositions are used in which the ratio of the photoconductive zinc oxide with respect to the zinc sulfide is gradually increased 10% by weight is reduced.

In addition to the photoconductive zinc oxide and zinc sulfide, the casting compositions contain per liter of solvent mixture the following ingredients:

Binder composition: ALKYDAL V 15 (trade name for

a styrenated alkyd resin from Bayer AG, West Germany) 16 g of 75% strength by weight solution of a copolymer of ethylene, vinyl sulfonyl chloride. and VinylcnLorLd (26.1 / 6.9 / 67 wt. - '$) in'L'oLuene. 80 y _t

Ura '/. Ol. O, Yd (<;

spectral sensitizers: bromophenol blue
and

28 mg

0 0

N-CH = CH-CH =

16 mg

Br '

0.2 ml

500 ml 30th ml 300 ml 170 ml

2 NH-COCH-

Silicone oil
Solvent mixture:

Dichloroethane

Ethanol

toluene

Methyl ethyl ketone

The total pigment content (ZnO + ZnS) is 400 g.
The ingredients are mixed in a ball mill.

The average grain sizes of the photoconductive zinc oxide and zinc sulfide are 0.17 microns and 1.8 microns, respectively.

A glassine paper support is made with the dispersion obtained

with a specific resistance of 5 · 10 0hm.cm at 50% relative humidity and a weight of 70 g per m2
dip coated. The whole is dried in a laminar air flow dryer by passing air at 40 ^° C. over the layer at a speed of 2 m per second. The applied layer contains 35 g of pigment per m2. ■

Column A of the following Table 1 contains the amount of zinc oxide of each casting composition, expressed in Gow .-% with respect to the total weight of zinc oxide and zinc sulfide.

DLo ßpaLte B contains analogous to column Λ the weight .- ',';> of zinc

209 R fi Γ »7

In column C the maximum positive charge is expressed by the obtained voltage level (V), built up under the the same, positive charge conditions.

In column D, the maximum negative charge, expressed by the voltage level (V) obtained, is built up under the the same, negative charge conditions.

In columns E and the percentage Έ, inherent dark decay for 3 seconds listed after the end of the positive or negative charge.

In columns G and H, the percentage drop is shown below same exposure conditions incandescent lamp (750 lux. sec.) for the positively and negatively charged recording layers. The drop in charge under exposure is measured, after a constant dark decay has been reached.

In column I, the relative sensitivity (expressed in steps) of the materials described is listed, which one by a negative corona charge, exposure by a Step wedge with constant 0.1 and development with positive electrophoretic toner.

Columns J and K ₄ show the contrast and image sharpness estimates of the results obtained in developing the positive charge images produced. In order to obtain these results after positive charging under the same conditions, the recording materials are exposed through a step wedge with a constant 0.5 and a transparent line original. Then the sharpness of the letters obtained is checked in the areas of different contrast.

2 0 9 B H!. / 1 ? 3?

GV .. ¹ Table 1 B.
(ZnS) C. D. E. .... G H I.
(Stages) J
(Contrast) K
(Sharpness) * I. VJl
VJl 0 210 800 86 F. - 87 11 no picture - ro A.
(2n0) 10 160 840 90 4th - 76 13th very weak bad 100 20th
30th 190
170 830
840 92
94 2 - 72
31 11
14th weak
weak bad
bad 2098 90 40 . 190 830 90 7th
9 - 20th 11 weak bad OO 80
70 50 360 840 89 4th 14th 11 Well bad 60 60 700 900 21 2 59 11 10 Well pretty good K) KJ 50 70 1000 840 8.2 2 11 13th 10 Well Well ♦ CO
. cn 40 80 1030 840 6th 2-5 6th 8th. 5. pretty good Well 0
co 30th 90
100 1040
1010 840
840 5
6th 2.4 5
2 6th
2 1
no quite
weak
no picture Well 20th 2.1
4th 10
0

Example 2

Example 1 is repeated, but with the difference that the zinc sulfide is replaced by barium sulfate (average Grain size: 1.7 microns), s

The results obtained are shown in Table 2 below to those of Table 1 listed and discussed.

GV. 557

Table 2

ο co 00 OD cn

(O

A.
(ZnO) B.
(BaSO ₄ ) C. D. E. F. G H Stages) J '
(Contrast) K
(Sharpness) 100 - 210 800 86 Vi - 87 11 no picture, - 90 10 760 850 22nd 94 68 16 weak bad 80 20th 820 840 18th 9 92 42 14th weak bad 70 30th 800 840 19th 12th 35 23 14th weak pretty good 60
50 40
50 810
840 840
840 18th
17th 14th
16 66
41 43
35 16
15th quite
Well
Well Well
Well 40 60 800 850 22nd 14th 33 31 14th Well Well 30th 70 760 860 21 17th 27 26th 11 Well Well 20th 80 700 840 25th 22nd 19th 18th 6th weak Well 10 90 700 840 24 24 10 10 1 weak Well 0 100 660 800 33 29 7th 7th no no picture -

_Λ

Example 5

Example 1 is repeated, but with the difference that the zinc sulfide is replaced by silica (average Grain size: 5 microns).

The results obtained are analogous to Table 3 below to those listed and discussed in Table 1.

557

2 0 9 8 H!) / 12 3 2

Table 5

CD
CO
OD

A.
(ZnO)

100

90

80

70

60

50

40

30th

20th

10

(SiO ₂ )

10
20th
30th
40
50
60
70
80
90
100

210 540

750 790 850 900 970

1020 950

1030

1150

800 86 830 78 840 27 840 27 85Ο 18th 840 12th 850 12th 830 10 840 13th 850 10 960 4th

5
8th
8th
9

11

11

16

19th

13th

97
97
96

63
53
25th
21

17th

87 90 90 75 77 95 95 40

29

19 2

Stages)

11 13 14 14 15 14 14 14

no

(Contrast J.

K (sharpness)

no picture

fairly weak fairly weak weak

weak

Well

Well

Well

pretty good

weak

no picture

no picture bad bad bad

bad chi real: uf

good good good no picture

CTi I

Example 4

Example Λ is repeated, but with the difference that the zinc sulfide is replaced by polyethylene particles with an average grain size of 15 microns.

The results obtained are analogous to those discussed in Table 1 for columns I, J and K and are hereinafter listed in Table 4.

Table 4

A.
(ZnO) B.
(Poly
ethylene). I.
(Stages) J '
(Contrast) [ ^K ■ '■'
¹ (sharpness) ^v 100 0 14th no picture ■ no picture 90 10 13th weak bad 80 20th 16 weak bad 70 30th 14th quite
weak bad · 60 40 19th Well bad 50 50 17th Well Well 40 60 15th Well Well 30th 70 7, Well Well 20th
10
0 80
90
0. 1
1
no quite,
Well
quite
Well
no picture Well
Well
no picture

Example 5

A homogeneous mixture containing the following ingredients

is produced in a sand mill: ■

Dichloroethane 7.4 liters

Ethanol 0.4 liters

Cyclohexane. 1 liter

GV.557

209885/1232

1 ,2 liters 240
1 ml
, 440 kg 2 , 160 kg 36 ml

50% strength by weight solution of the terpolymer of vinyl acetate, styrene, aliphatic Acrylic acid ester and acrylic acid (25/30/44/1% by weight) in toluene -

ALKTDAL V 15 (trade name) as a 75% strength by weight solution in toluene

Zinc oxide, type ELEKTROX (trade name)

colloidal silica (average particle size 5 u)

10% strength by weight solution of urazole in dimethylformamide

1% strength by weight solution of bromophenol blue

in methanol - 19 ml

0.5% by weight solution of the cyanine

sators from Example 1 in dimethylformamide 22 ml

The dispersion is applied with rollers in a ratio of 40 g solids per m2. The applied layer is dried in a laminar airflow dryer. As carrier Glassine paper of 72 g per m2 is used for the applied layer, containing sodium sulphate and calcium chloride has been made more conductive.

After charging with a positive corona, the recording layer is covered by a negative, transparent line master exposed and developed in an electrophoretic developer with the following composition:

5OO g Alkydal L 67 (trade name of Farbenfabriken Bayer AG, Leverkusen, Western Germany, for a LeinSl (67 parts by weight 90 modified alkyd resin) and 500 ml of white spirit, of 11 wt .-% contain aromatic compounds, are heated to 6O ⁰ C until a clear solution A is obtained. After solution A has cooled to room temperature, 150 g of it are used as a fixing agent for the following dispersion:

Carbon black (average particle size: 20 mp) 30 g Zinc monotridecyl phosphate 1.5 g

SHELLSOL T (trade name for a mixture of aliphatic hydrocarbons, the following Have properties:

Density at 15 ° C: 0.764 Boiling range: 180-200 ⁰ C Viscosity at 25 ° C: 1.62 cP

Kauri butanol number (KB): 31) 750 ml

* ^PP '209885/1232

Mixing solution A with the composition is done as

follows:

150 g of the solution are first in a ball mill with 1.5 g of the zinc monotridecyl phosphate, whereupon 30 g of Buss and at least 750 ml of SHELLSOL T (trade name) are added.

After this composition has been milled for 15 hours the concentrated developer obtained with SHELLSOL T (trade name) diluted in a ratio of 15/1000.

The developer thus obtained is very stable and gives after the solvent is evaporated from the recording layer is., extremely erasable pictures.

This gives a high contrast image with excellent sharpness, that the ^terms: shows the original reverse image values.

Example 6,.

It becomes a homogeneous mixture of the following ingredients

made in a sand mill:

Dichloroethane 2.3 liters

Ethanol 0.3 liters

Toluene "-2.3 liters

n-butanone 1.7 liters

'ALKIDAL V 15 (trade name) as 75% strength by weight solution in toluene 210 ml

ZnO type MICEOX (trade name) 1.6 kg

Silica (average particle

size 5 μ). ■ 2.4 kg

HYPALON 30 (trade name for the copolymer ethylene / vinylsulfonyl chloride / Vinyl chloride (26.1 / 6.9 / 67 in% by weight),

traded by E-.I. du Pont de Nemours ". · & Co. (Ind.), Wilmington, Del. USA) as a 25% by weight solution in dichloroethane 4.6 kg

a 3% by weight solution of silicone oil

in dichloroethane 66 ml

The dispersion obtained is applied and treated further as described in Example 5.

A high-contrast image is obtained which shows image values which are reversed with respect to the original.

^GV ' ⁵⁵⁷ 209 885/123 2

Claims (1)

Patent claims 'Electrophotographic recording material, characterized in that that it contains a photoconductive binder layer which is a mixture of photoconductive zinc oxide particles and colorless or white, positively chargeable pigment particles in a weight ratio, that is less than 50:50 »but not less than 10:90 . 2. Electrophotographic recording material according to Claim 1, characterized in that the positively chargeable pigment particles are zinc sulfide particles. 3 · Electrophotographic recording material according to claim 1, characterized in that the positively chargeable pigment particles are barium sulfate particles. 4-. Electrophotographic recording material according to claim 1, characterized in that the positively chargeable pigment particles are silica particles. 5 · Electrophotographic recording material according to claim 1, characterized in that the positively chargeable pigment particles are polyethylene particles. 6. Electrophotographic recording material according to each of the preceding claims, characterized in that the photoconductive layer is the particles that are in a insulating binders are dispersed in such a way that the layer contains from 50 to 97% by weight of dispersed particles η contains and a specific resistance between 10 'and 14th
10 ohm. Cm. 7. An electrophotographic recording material according to claim 6, characterized in that the ratio of the binder to the dispersed particles is between Λ-Λ and 1:10 parts by weight. GV.557 209885/1232 . - ■ - 21 - ■ 8. Electrophotographic recording material according to each of the preceding claims, characterized in that the zinc oxide particles in combination with an acid ester derivative an oxo acid of phosphorus can be used. 9 · Electrophotographic recording material according to each of the preceding claims, characterized in that the zinc oxide particles are used together with a compound which corresponds to the following general formula (including its SaIζstructures and tautomeric Structures): in which: E ^ l and Ep each have a hydrogen atom, including an alkyl group .a substituted alkyl group, an aryl group including a substituted aryl group, an acyl group including a substituted acyl group or a heterocyclic compound including a substituted, heterocyclic ring, or E / | and Ep together represent the necessary atoms a fused in or an fused in system to build, . Z denotes the atoms that are necessary to close a 5- or 6-membered, heterocyclic ring, including such a ring in substituted form and including such a ring which is part of a substituted or unsubstituted, fused-on ring system ,
X is an oxygen atom or imino, where at least one of the nitrogen atoms which are part of the ring closed by Z is hydrogen atom carries. 10. Electrophotographic recording material according to each of the preceding claims, characterized in that the size of the dispersed particles is between 10 microns and 50 microns varied. GV 557 209885/1232 11. Electrophotographic recording material according to each of the preceding claims, characterized in that the photoconductive layer has one or more compounds includes to their general sensitivity and / or their Increase sensitivity to rays in a specific part of the spectrum. 12. Electrophotographic process for producing an arbitrarily positive or negative reproduction of a Originals by means of (1) the same photoconductive recording material and developing material as a electrical charge sign (positive or negative) and (2) by the choice of the charge sign of the electrostatic charge on the photoconductive recording layer of the photoconductive recording material is given, characterized in that a photoconductive Recording layer is used which has a Mixture of photoconductive zinc oxide particles and colorless or white, positively chargeable pigment particles in one Includes weight ratio that is less than 50:50, but is not less than 10:90. 15. Electrophotographic method according to claim 12, characterized in that marked that a microfilm image is used as the original. 14. Electrophotographic process according to claim 12, characterized in that an optical magnification exposure of the recording material is applied. 15. Electrophotographic process according to any one of the claims 12 to 14, characterized in that a photoconductive Zinc oxide which has been treated with urazole or a urazole derivative, in which at least one the ring nitrogen atom carries a hydrogen atom is used will. GV.557 209885/1232